Time is key for weight loss, study finds

New research done on mice shows the longer one stays overweight, the more likely it becomes for them to regain weight lost.

Obesity 370.
(photo credit:Wikimedia Commons)

ANN ARBOR, Mich. — Joint research between the University of Michigan and
the Argentina-based National Council of Science and Technology
(CONICET) has shed light on one of the most frustrating mysteries of
weight loss – why the weight inevitably comes back.

A novel
animal model showed that the longer mice remained overweight, the more
“irreversible” obesity became, according to the new study that appeared
online recently in the Journal of Clinical Investigation.

Over
time, the static, obese state of the mice reset the “normal,” body
weight set point to become permanently elevated, despite dieting that
initially worked to shed pounds, authors say.

“Our model
demonstrates that obesity is in part a self-perpetuating disorder and
the results further emphasize the importance of early intervention in
childhood to try to prevent the condition whose effects can last a
lifetime,” says senior author Malcolm J. Low, MD, PhD, professor of
molecular and integrative physiology and internal medicine.

“Our
new animal model will be useful in pinpointing the reasons why most
adults find it exceedingly difficult to maintain meaningful weight loss
from dieting and exercise alone.”

The lead author of the study was Viviana F. Bumaschny, MD, assistant investigator of CONICET.

Obesity
affects more than 500 million adults and 43 million children younger
than age 5, while related illnesses are the leading preventable cause of
death.

Individuals who are overweight have a much higher risk of type 2 diabetes, hypertension, and cardiovascular diseases.

One
of the major strengths of the research was a new model of
obesity-programmed mice that allowed weight loss success to be tracked
at different stages and ages by flipping a genetic switch that controls
hunger.

Turning on the switch right after weaning prevented the
mice from overeating and ever becoming obese. Similarly, mice that
remained at a healthy weight into young adulthood by strict dieting
alone were able to maintain normal weight without dieting after turning
on the switch. However, chronically overfed mice with the earliest onset
of obesity never completely returned to normal weight after flipping
the switch, despite marked reduction in food intake and increased
activity.

The new findings may raise questions about the
long-term success rate of severe calorie restriction and strenuous
exercise used later in life to lose weight, such as the extreme regimens
seen in the popular reality television show “Biggest Loser.”

“Somewhere
along the way, if obesity is allowed to continue, the body appears to
flip a switch that re-programs to a heavier set weight,” Low says. “The
exact mechanisms that cause this shift are still unknown and require
much further study that will help us better understand why the regaining
of weight seems almost unavoidable.”

The findings will be
published alongside a corresponding commentary “Tipping the scales
early: probing the long-term effects of obesity.”